da850evm: add support to read mac address from SPI flash

add support to read mac address for da850/L138 evm manufactured by
Logic PD which store mac address in SPI flash manufactured by ST
Microelectronics. This patch adds support to read mac address from
SPI flash and set the mac address if it hasn't been set in environment,
If it has been set in the environment it compares the value one with
SPI flash and warns on mismatch. Introduced a config option
CONFIG_MAC_ADDR_IN_SPIFLASH indicating where to look mac address for.

Signed-off-by: Manjunath Hadli <manjunath.hadli@ti.com>
Cc: Tom Rini <trini@ti.com>
Cc: Mike Frysinger <vapier@gentoo.org>
Cc: Wolfgang Denk <wd@denx.de>
diff --git a/boards.cfg b/boards.cfg
index 05ce1ae..5610daf 100644
--- a/boards.cfg
+++ b/boards.cfg
@@ -121,7 +121,7 @@
 cam_enc_4xx                  arm         arm926ejs   cam_enc_4xx         ait            davinci     cam_enc_4xx
 da830evm                     arm         arm926ejs   da8xxevm            davinci        davinci
 da850_am18xxevm              arm         arm926ejs   da8xxevm            davinci        davinci     da850evm:DA850_AM18X_EVM
-da850evm                     arm         arm926ejs   da8xxevm            davinci        davinci
+da850evm                     arm         arm926ejs   da8xxevm            davinci        davinci     da850evm:MAC_ADDR_IN_SPIFLASH
 davinci_dm355evm             arm         arm926ejs   dm355evm            davinci        davinci
 davinci_dm355leopard         arm         arm926ejs   dm355leopard        davinci        davinci
 davinci_dm365evm             arm         arm926ejs   dm365evm            davinci        davinci